Lock Timeouts (timeout > 0)/sec is part Locks counter part of the SQLServer:Locks object.Accrding to BOL : “Number of lock requests per second that timed out, but excluding requests for NOWAIT locks”

It is not uncommon to monitor on lock timeouts . The can cause bottlenecks and it is important to identify queries which cause these timeouts. The overall objective is to decrease the amount of time a lock is held. The goal is to have 0 during normal Production time.

One of the resources SQL Server can lock out on is Extent. A lock on a contiguous group of 8 pages.